1. Field
Exemplary embodiments of the present invention relate to a method for fabricating a semiconductor device, and more particularly, to a method for fabricating a semiconductor device with a side contact.
2. Description of the Related Art
A planar channel transistor has reached the physical limit in reducing a leakage current, an on-current, and a short channel effect, which are caused by the shrinkage in the size of a memory device, and thus it becomes more difficult to reduce the size of the memory device. Therefore, a vertical channel transistor has been developed. A buried bitline (BBL) having a metal layer is formed to make a cell with the vertical channel transistor. Since the buried bitline is connected to a part of a sidewall of an active region forming a vertical channel, a side contact is desired to be formed.
The cell of the memory device forms a bitline contact between a buried bitline including a metal layer and an active region. For the bitline contact, a contact open process of exposing one sidewall of an active region is performed. The bitline contact is formed by a side contact structure of exposing one sidewall of the active region.
FIG. 1 is a diagram illustrating a semiconductor device in the conventional art.
Referring to FIG. 1, a plurality of active regions 12 are formed on a substrate 11. The active regions 12 are separated by trenches 13 at a regular distance. A hard mask layer 14 is formed on the active regions 12. A buried bitline 16 is formed in the trench 13. The buried bitline 16 is electrically connected to a part of one sidewall of the active region 12. An ohmic contact region 15 is formed in an interface between the buried bitline 16 and the active region 12.
A contact process is performed in order to connect the buried bitline 16 to a part of one sidewall of the active region 12. This process will be referred to as one side contact (OSC) process. The OSC process is also called a ‘side contact process’. A side contact region 19 is formed by etching a part of first and second liner layers 17 and 18.
However, in the conventional art, since the active region 12 has a high aspect ratio, it is difficult to form the side contact region 19 at a desired portion of the sidewall of the active region 12. Furthermore, it is difficult to ensure the uniformity and reproduction characteristics of the side contact region 19.